1. Field of the Invention
The present invention relates to a robot program changing device that changes an operational program for a robot so that the robot performs a desired movement.
2. Description of the Related Art
Generally, a robot operational program that is created offline is rarely used in an actual situation without correction, and is used after correction. This is because a relative positional relationship between a workpiece and a robot, a posture of a robot, and the like subtly differ between an offline world and an online world (actual situation), and such differences occur.
As described in Japanese Unexamined Patent Publication No. 2007-54942, a load of a motor of a robot is obtained by simulation, and on the basis of the obtained load, a command speed or a command acceleration of an operational program is changed to eliminate the above-described differences.
Moreover, in some cases, a smooth operation is taught. Thereby, while a deceleration is started for positioning at a certain teaching point indicated by one operational command, an acceleration is started for moving to another teaching point indicated by a next operational command to smoothly connect movements indicated by two operational commands.
FIGS. 12A to 12C are illustrations for explanation of the smooth operation. When the smooth operation is not taught, as illustrated in FIG. 12A, in a duration D1 of a movement command in a first block B1, a robot accelerates at a predetermined acceleration, and in a duration D2, the robot similarly decelerates to arrive at a teaching point P. Then, in a duration D3 of a movement command in a second block B2, the robot accelerates again to start to move toward another teaching point. In this case, the robot moves on a trajectory drawn by the solid line in FIG. 12C.
On the contrary, when the smooth operation is taught, as illustrated in FIG. 12B, at the time of the start of the duration D2, a robot starts to decelerates for the first block B1, and starts to accelerate for the second block B2. For this reason, at the end of the duration D2, the robot stops the decelerating operation for the first block B1, and stops the accelerating operation for the second block B2. Accordingly, when the smooth operation is taught, as illustrated in FIG. 12C, the robot can smoothly shift from the first block B1 to the second block B2.
As illustrated by the solid line in FIG. 12C, when the smooth operation is not taught, the operational command for the first block B1 causes the robot to arrive at the teaching point P. However, when the smooth operation is taught, as illustrated by the broken line in FIG. 12C, the trajectory in which the robot does not pass through the teaching point P is formed. Accordingly, teaching the smooth operation possibly causes an actual movement path of the robot to depart from a target movement path.
On the contrary, when the smooth operation is not taught, teaching points are connected to each other so as to form the shortest line, and an actual path of the robot does not depart from the target movement path. However, when the smooth operation is not taught, a cycle time can increase, as indicated by comparison between FIG. 12A and FIG. 12B.
In view of the above-described problem, the present invention was made. An object of the present invention is to provide a robot program changing device that changes an operational program so as to enable a robot to move via an original teaching point while decreasing a cycle time of the operational program, even when a smooth operation is taught.